[gentoo-dev] Support for multiple ABIs for amd64 (64bit,32bit) in multilib overlay

[Thomas Sachau]

Let me introduce a nice project, which was started by some users:

Since the emul-linux-x86-* packages for 32bit libs for amd64 users are neither easy to maintain nor
up-to-date, some users started to implement an eclass, which allows to build requested libs with
additional 32bit support. Later i joined them and helped them improving it a bit, but it was and
still is mainly their project, they do the main work keeping this overlay up-to-date.

Also this overlay is a nice idea to drop emul-linux-x86-* packages, it either requires continual
work or modification of many ebuilds in main tree to support this in long term. To avoid this, i
took the original multilib portage patch from kanaka, adjusted it to the current portage code and
added the ideas and code from the eclass version. The result is now a portage, which is able to
build any ebuild with additional 32bit lib support.

The current main regression are ebuilds and eclasses, which do not support this (e.g. perl modules
and mysql).

If anyone is interested:

-for the eclass version, which is mainly maintained by users and is mainly intended to only replace
the emul-linux-x86-* package: just add it via "layman -a multilib" (it should be pretty stable and
mostly working).

-for the portage version: It is also in the multilib overlay, but in a different branch called
portage-multilib. To use this, you should read the instructions at [1]
(doc/portage-multilib-instructions). This one should also mainly work, but there is probably a good
amount of packages in the main tree, which may refuse to work with it.

Bugreports: preferred way is #gentoo-multilib-overlay at irc.freenode.org, but we also have an
alias, where you can contact us: multilib@g.o

[1]: http://github.com/sjnewbury/multilib-overlay/tree/portage-multilib
-- 
Thomas Sachau

Gentoo Linux Developer